Stack protector: leak of guard's address on stack

[Florian Weimer]

* Maxim Kuvyrkov:

> The problem is fairly target-dependent, so architecture maintainers
> need to look at how stack-guard canaries and their addresses are
> handled and whether they can be spilled onto stack.
>
> It appears we need to poll architecture maintainers before filing the CVE.

One CVE ID by identified affected architecture would work as well.
MITRE cares about affected software *versions* as well, and since the
targets were added at different GCC versions (or stack protector
support was added), the CVE IDs should be split in most cases anyway.